1. Field of the Invention
The present invention relates to a font data compression method in a character generator.
2. Description of the Prior Art
In a conventional character generator such as an electronic computer, a Japanese word processor and the like, a ROM stores a whole configuration of font patterns for forming a variety of letters and graphic characters as dot matrix data. On the occasion of printing and graphic display, the graphic characters and letters corresponding to input codes are regenerated from the data of the ROM. With an increase in the number of built-in fonts, however, a storage capacity of the ROM for storing the dot matrix data is increasingly large. Prices of those equipments are forced to increase.
A character pattern compression method disclosed in Japanese Patent Laid-Open No. 66290/1985 was proposed as a method of storing a multiplicity of letters and graphic characters without changing the storage capacity of the ROM. Based on this method, the dot matrix data representing the whole configuration of the font patterns are divided into a multiplicity of windows to detect an inversion or non-inversion of the dot data. More detailed data are prepared for the windows in which the dot data is inverted, thereby obtaining data per hierarchy. Those data are finally totaled, and the font pattern are thereby regenerated. For this reason, the configuration becomes complicated. When applying such a font pattern that the dot data is frequently inverted, this causes a defect of requiring a greater number of data than in the case of effecting no data compression on the whole.
The font data themselves for forming the font patterns can be thinned out by applying a character font degree transform method disclosed in Japanese Patent Laid-Open No. 116890/1984. If such a method is employed, there arises a problem of deteriorating a resolution of the regenerated font patterns. This method is also unsuitable for regenerating the font patterns assuming an intricate configuration.